Juliana Young Koo’s family began giving birthday parties for her in 1995, when she turned 90. Ten years later, she took the microphone and addressed the crowd.

“I never give speeches, but I decided that at least on my 100th birthday, I should try,” she wrote in her autobiography, “My Story” (2009). “I have only one secret: That is, THINK POSITIVELY. Don’t dwell on the past; think about how to make the future better.”

It was advice Mrs. Koo followed again and again — when her first husband was executed by the Japanese in the Philippines; when she became seasick on the ship that brought her to the United States after the war (she said it had almost capsized in a violent storm); and when thieves stole her jewelry after she had moved to New York.

She adapted to circumstances as she lived a long, sometimes adventurous, life of travel, good works and glamour, moving in diplomatic circles, attending a swirl of parties, all the while witnessing a century of history.

By 2012, when she celebrated her 107th birthday, guests marveled that she had been born the year that Theodore Roosevelt began his second term as president, the year the Russo-Japanese War ended, the year Einstein worked out the theory of special relativity.

Mrs. Koo died on May 24 at her home in Manhattan after a mah-jongg party — the tile game became her passion in later years — and a birthday celebration for her daughter Shirley Young. Mrs. Koo was 111.

Genevieve Young, another daughter, confirmed her death.

Mrs. Koo was born Yu-Yun on Sept. 27, 1905, in Tianjin, in northeastern China, according to her autobiography. Her father, Yen Yi-ping, was a businessman.

She entered the Keen School, run by Methodists, when she was 14. “At missionary schools with English-speaking teachers,” she wrote in her autobiography, “one had to have an English name.”

She added: “The school named me ‘Helen,’ but there was already a Helen Yen at the school, so I renamed myself ‘Juliana.’ I can’t remember why. I must have read it in a book.”

She enrolled in Shanghai Baptist College in 1925 and became known as “Miss 84,” for the license plate on her car, a number that could be translated as “love and luck” in Chinese, she wrote. But she found the school too strict and transferred to Fudan University, which had just begun to admit women.

Her first husband, Clarence Kuangson Young, was a diplomat who, in the late 1930s, was posted to Paris and then to Manila, as consul general to the Philippines. Mrs. Koo wrote in her autobiography that his “main mission” there was to “raise money from the Chinese community for the war against the Japanese.” She pitched in, as honorary chairwoman of the Overseas Chinese Women’s Association, organizing drives to collect jewelry that could be sold.

The Japanese arrested her husband and his staff in 1942. Mrs. Koo took in the others’ families — cramming more than 25 people into a three-bedroom bungalow.

After the war, she was told that the Japanese had executed her husband. The analyst and commentator Paul French wrote in “Through the Looking Glass: China’s Foreign Journalists from Opium Wars to Mao” (2009) that Mr. Young had “stuck to his post even after the retreat of General Douglas MacArthur to Australia and the surrender of the American troops.”

“He apparently had the chance to leave with MacArthur’s party” but did not, Mr. French wrote.

Mrs. Koo left for California with her children in 1945, intending to settle in San Francisco. But after arriving there, she realized that she knew more people in New York, so she and the children headed east by rail on the Twentieth Century Limited. She soon heard about an opening for a protocol officer at the United Nations, then in its infancy.

She worked for the United Nations for 13 years, until shortly after she married Dr. V. K. Wellington Koo, who had been the Chinese ambassador to the United States. They moved to the Netherlands after he was appointed to the International Court of Justice in The Hague in 1960. He served until 1967. He died in 1985 at 97.

One ritual at Mrs. Koo’s birthday parties was the taking of a photograph. As the years passed, there were more faces to fit in: children, grandchildren, great-grandchildren. Mrs. Koo was typically at the center of the frame, flanked by her daughters Genevieve, who is known as Gene and was vice president and editorial director of Bantam Books, and Shirley, a former vice president of General Motors and a founding member and governor of the Committee of 100, a Chinese-American leadership group.

Both daughters survive her, with her seven grandchildren; 18 great-grandchildren; four stepchildren; 13 step-grandchildren; 18 step-great-grandchildren; and two step-great-great-grandchildren. A third daughter, Frances Young Tang, who was known as Baby, died.

At the party in 2012, Mrs. Koo was still quite spry, and evidently still thinking positively. She danced with Oscar L. Tang, a financier and the widower of her daughter Frances, as the band played “Moon River.” Mr. Tang had requested a leisurely tempo, but Mrs. Koo would have none of that. As he recalled, “She said, ‘Faster, this one’s too slow.’”